This invention relates to a detonator control method of the electronic ignition module type, as well as to an encoded firing control assembly and to a ignition module for its implementation.
In most works involving explosives, the bursters containing the detonators are caused to detonate according to a very accurate time sequence, in order to improve the working yield of the explosive and to better control its effects.
Conventionally, a pyrotechnic device at the level of the detonators themselves enables to obtain various delay times between the explosions of the bursters. The detonators are actuated simultaneously by an exploder which delivers a certain electric energy to a firing line linking the detonators, in series or in parallel. The combustion of retarding pyrotechnic compounds then generates the requested pyrotechnic delays.
However, these pyrotechnic delays often exhibit insufficient relative accuracy.
To overcome this shortcoming, it has been suggested to use integral delay detonator ignition devices of the electronic type. Such devices enable to take advantage of the accuracy of electronic systems to enrich and to fine-tune the delay time ranges obtained previously in a pyrotechnic manner.
The application for patent FR-2.695.719 suggests a detonator control method with an integral delay electronic ignition module in which the ignition modules can be programmed using a programming unit. They call for an accurate time basis at the level of each detonator.
It has also been suggested in the patent U.S. Pat. No. 4,674,047, to use detonators fitted with electronic means enabling them to establish a dialogue with an external control unit. Each detonator is fitted with a capacitor whose discharge actuates the burster. The delay times of each detonator can be programmed on-site, whereas an identification code has been ascribed previously to each detonator, for example when leaving the factory. During a firing sequence, the detonators receive from the control unit successive orders, first to discharge the capacitor above mentioned, then to fire. They send back to the control unit, pieces of information enabling this unit to check the firing sequence for correct operation. The detonators are fitted to this view with a microprocessor-based local intelligence. The delay times which have been ascribed to the said are stored on non-volatile memories in their microprocessors.
In this last known system, each of the detonators has an internal time basis enabling it to perform a countdown in relation to the delay time which it has been ascribed. At the time of programming the detonator, its time basis is compared to a reference time basis for the control unit. Any possible error is then compensated for by a delay time adjusted value, whereby this adjusted value is stored in a memory of the detonator.